64GB Extreme SDXC UHS-I card speeds?

Hi guys,

Just received my new SD card I bought because of the up to 45MB/s speeds for HD Video.

Decided to test it with:

H2testw 1.4                                                      Write: 20.6MB/s            Read: 21.6MB/s

CrystelDiskMark 3.0.2 x64                            Write: 22.36MB/s          Read: 23.76MB/s

I’m sorry, but it doesn’t make any sense to me. Spend extra money to get fast card and all I got is Ultra with Extreme label on it!

Is there anyone, who can explain this to me, please?

Thank you for your help.

Kind regards


Could be the reader or USB port you’re using that is causing the slower speeds.

these cards are based off the newest SD spec SD 3.0. They are UHS cards (Ultra High Speed) and require a UHS compatible reader. You will also need a USB 3.0 port to get the full speed. The SanDisk Imagemate SDDR-289 is the reader you will need to use. 


On a similar query : I purchased San Disk Extreme sdxc UHS-3 .

SanDisk 64 GB Extreme Micro SD XC Memory Card For Go Pro Hero 4 4k HD U3 90MB/s

I ran this through a test using h2testw 1.4 on a win 7 sony netbook with integral card reader via an adaptor.

The speeds i obtianed were approx 19MB/s write and 20 MB/s read.

The capacity is good and has been read and verified to.

Only issue i think i have is speed. I thought the minimum was  30MB/s for this card?

Is this reasonable given the specs above? I was expecting it to be closer or above 30. Otherwise it seems OK.

Based on the above is this reasonable performance v the spec.?

Using it on Android Tablet has not presented any issues , it is beiing recognised by SD Insight it reads as a San Disk SE64GB.

Uisng Android app > A1 SD Bench on my UK -Tesco Hudl 2 Tablet 1.83 GHZ v5.1 Lon benchmark were

R 21.04 MB/S. w 21.02 MB/S

Yes - i probably should have taken more time to source. The one i purchased from may or maynot be approved but he had good feedback. 

Any comment or advice that you can give myself and any other readers.

 Thankyou in advance for reading and any response.

Having websearched i couldnt find any info on the card reader speeds on older devices i have. 

My speed result on a U3 spec are pretty much the same as a U1 on two devices. So it being a  upper level limitation elsewhere sounds plausible given older hardware.

Thanks for the pointer re the card reader.ormative

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